Insurance for your first year on your own policy, particularly if you're under 20 is always going to be expensive.
My first policy was about £1200 for a 19yr old on a Mk2 1.8 GL, (not even a GTI), even though I had been driving for 2 years, but I hadn't got any no claims bonus.
Being a named driver on someone elses policy will always be cheaper (if they're older/more experienced) because it's assumed that they will be driving the car more often, so the risk will be less, hence cheaper insurance.
If going for your first policy, try doing quotes with you as main driver, but adding one or both parents (particularly if they're over 40 or 50) should knock it down a bit.
Nobody would like it, but try doing quotes with and without the mods, to see if that effects the quote much (Admiral/Elephant are good for trying out different mods on quotes) and if it's significantly cheaper without the mods, take them off the car (driving a car with mods when they aren't declared on the policy will invalidate your insurance). Mods like alloys make the car more desirable, thus a higher risk for theft. Also make sure you're only quoting for Third Party Fire and Theft, some online quotes assume that you want Fully Comp until you tell them otherwise, it's not worth getting Fully Comp on a Mk3 1.6 CL as it's only worth about 7-800 and your excess on any Fully Comp claim will be several hundred pounds.
My insurance this year on a Mk3 1.8 CL (the 75bhp engine) was about £400 for TPFT with no mods, 4yrs no claims, 9yrs driving, but with a learner driver, from Swiftcover, by far the cheapest. I had several quotes over a grand and one around £1500.